Optoelectronic devices generally include light-emitting devices and photovoltaic devices. These devices generally include an active layer sandwiched between two electrodes, sometimes referred to as the front and back electrodes, at least one of which is typically transparent. The active layer typically includes one or more semiconductor materials. In a light-emitting device, e.g., an organic light-emitting diode (OLED), a voltage applied between the two electrodes causes a current to flow through the active layer. The current causes the active layer to emit light. In a photovoltaic device, e.g., a solar cell, the active layer absorbs energy from light and converts this energy to electrical energy exhibited as a voltage and/or current between the two electrodes. Optoelectronic devices may be produced by various means. One approach is to use vacuum deposition of semiconductor materials, and a second approach is to use solution processed materials. Various substrates including glass and plastic film can be used as a base for depositing the layers on. Alternately, the optoelectronic device may be built using the opaque layer (metal or polymer or ceramic) as the substrate and an alternate build sequence is employed. Regardless of the construction of the device, it is necessary to provide an encapsulating hermetic package to protect it from the deteriorating effects of moisture and oxygen exposure. The package must also provide electrical interconnections in a feedthrough configuration to connect a power supply that is external to the package.
OLEDs are produced in a flat thin format for use as displays or for general illumination. The use of a plastic substrate provides the thinnest and most flexible configuration, and also the potential for low cost roll-to-roll production. Accordingly, there is a need for packaging technology that is also thin and flexible, and preferably amenable to roll-to-roll production coincident with the OLED fabrication. The package should be suitable for large area (up to about one or more square meters) displays or luminaries for particular applications.
Barrier films, referred to as ultra high barrier (UHB) films or UHBs, are used for direct fabrication of OLEDs and other optoelectronic devices. These films typically consist of a thin transparent oxide layer on a transparent plastic film, for example, as described in U.S. Pat. No. 7,015,640, U.S. Pat. No. 7,154,220, and U.S. Pat. No. 7,397,183 assigned to the General Electric Company. However, the barrier films can be damaged in handling, so that fabricating a device directly on the barrier film may degrade its performance and create a moisture ingress path. In addition, moisture and oxygen can permeate laterally through adhesive layers at the edges of the device and also through the adhesive that seals the electrical wire feedthroughs. Moreover, intrinsic moisture in the adhesive and substrate materials can damage the device. The package design must be compatible with low cost materials and continuous roll-to-roll production, and the material set must be low cost and suitable for high speed processing. Thus, there is a need for an improved thin flexible packaging technology for expanded application of low cost production of OLEDs and other optoelectronic devices. U.S. application Ser. No. 12/470,033, filed 21 May 2009 describes methods for packaging optoelectronic devices utilizing a piece or sheet of conductive material covering feedthrough apertures in a barrier layer to couple electrodes of an optoelectronic device to electrical interconnectors, and ultimately to a power supply. However, improved methods and materials for manufacturing the patch and coupling the patch to the electrodes are desirable.